Vibration testing of components such as electronic equipment used in aircraft and rockets, for example, is well-known. A common type of vibration testing equipment involves a shaker table on which the component to be tested is mounted. The shaker table is then oscillated along a horizontal axis, for example, at a selectable frequency by a mechanical oscillator or exciter. The oscillating table is supported on a type of bearing surface which allows the table to oscillate relative to a supporting base. The mechanical oscillator is also mounted on this same base.
Such a horizontal vibrator forms a dynamic system in which each component affects the vibration level to which the test article is subjected. At certain frequencies of the mechanical oscillator, the vibration level or displacement amplitude of the shaker table and test article may diminish due to the dynamic properties of the exciter and/or the reaction base on which the exciter is mounted. Because the base is not a perfectly rigid mass, bending oscillations may be set up in the reaction base by the exciter in such a way that the test article remains almost stationary while the mechanical oscillator and reaction base oscillate relative to the test article.